The invention set forth in this specification pertains to new and improved rotary pistons. These pistons are constructed for use with rotary piston rods such as are employed in connection with various machines for cleaning tubes and pipes in chemical process and other related industries.
Such machines are normally constructed so as to include an elongated cylinder holding a piston in such a manner that a non-round piston rod rotatably connected to the piston can be moved axially with respect to the cylinder out through a rotary seal at one end of the cylinder. A conventional motor and mechanical coupling is normally employed in such a machine in order to rotate the piston rod as the piston is moved internally within the cylinder so as to both rotate and reciprocate a cutting or cleaning tool mounted on the end of the rod remote from the cylinder. A cutting or cleaning tool is moved in this manner within the interior of a tube or pipe so as to remove various types of deposits and accumulations from the interior of such a tube or pipe.
Many of such accumulations or deposits are of an extremely hard, tenacious character. As a consequence of this it is frequently quite difficult to break up or dislodge such deposits or accumulations during the use of a machine as indicated in the preceding discussion. The effective removal of such hard, tenacious deposits requires that comparatively large forces be applied to the piston in a machine as indicated in order to move the cleaning or cutting tool along a linear path. The removal of such deposits also requires the use of comparatively large amounts of power in rotating the piston rod employed. Such comparatively high amounts of power can, of course, be achieved in various different manners.
The most obvious of these would be to construct machines as indicated in the preceding discussion in a comparatively large, massive manner. This is considered to be disadvantageous because such machines have to be moved from one location to another in cleaning various different tubes and pipes. As a consequence of such movement such machines should be as small and light in weight as reasonably possible. In order to achieve this combination of light weight in a machine which is capable of removing comparatively hard, tenacious deposits such machines have been constructed so that the pistons in them have been operated by comparatively high pressure hydraulic fluids such as fluids in the pressure range of about 4,000 to 5,000 psi pressure.
The use of such comparatively high pressure hydraulic fluid in machines for cleaning tubes and pipes has proved somewhat disadvantageous for a rather unexpected reason. The pistons used in such machines have tended to wear out or fail after comparatively short periods, presumably because of the high pressures involved but in addition probably because of the comparatively high temperatures encountered or developed as a result of the use of such pistons when hydraulic fluids at such pressures are applied to such pistons. It is considered that a significant part of the temperature buildup tending to affect piston life is the result of the rotation of the piston rod used in connection with such a piston.